From Bulbapedia, the community-driven Pokémon encyclopedia.
Jonah is a male homo sapien (i.e., a human boy) who was introduced to Pokémon at age 6 (summer of 1999), when a kid named Paul offered him a Pokémon card. Paul said that Jonah had to trade another card for Paul's Charmander card (First Pokémon ever seen by Jonah. He thought it was cute), so Jonah took a Meowth card instead. He still has it.
Jonah claims to dislike the Pokémon anime, but still considers some episodes worth watching, especially DP episodes. Jonah plays the video games 24 hours a day, 6 days a week, and has a huge amount of Pokémon cards that he refuses to throw away or sell, despite not actually touching them for years. He also is interested in the PokéSpecial manga.
He is immensely interested in small details in video games and other things that nobody ever notices or cares about, side games, glitches, the actual plot of games and game music (As opposed to buying Pokémon just for competetive battling. Jonah currently dislikes competetive battling, although he might try to EV train some Pokémon in the future), and long and difficult words like floccinaucinihilipilification (noun, the act of considering something or describing something as worthless).
Jonah has mycophobia (Fear of mushrooms).